1. Field of the Invention
The field of the present invention is that of turbine engines and, more particularly, that of devices for holding compressor blades for said turbine engines.
2. Description of the Related Art
Turbine engines generally comprise one or more compressors designed to compress the air drawn into the air inlet, before its introduction into the combustion chamber where it is used to burn the injected fuel and to provide the desired propulsion. The compressor blades are essentially of two types as regards their manner of attachment to the corresponding hub. Some blades have a so-called shank fastener, i.e. they are held on the hub by a part which is inserted in a housing provided to this end; others have a hammer-type fastener, i.e. the shape of the root of the blade is flared, forming a bulb shape which is slid into a circumferential peripheral groove recessed in the external face of the rim of the hub. In this latter case, said rim has a recessed, semi-circular cross section, surmounted by two shoulders, of which the internal face has a support surface, commonly denoted the bearing surface, which is used to hold the blade when centrifugal force is applied.
The blades are successively inserted by their roots into said peripheral groove, or fastener, until it is completely filled. To engage the blades in the peripheral groove an insertion notch is formed in the lateral shoulders through which the bulb-shaped ends of the roots of the blades may pass. A locking device is provided to hold the last blade(s) introduced, which is(are) located opposite this notch, and to prevent them from coming out again. This device generally also has the function of retaining the set of blades in circular rotation and preventing them from being driven by the action of aerodynamic forces which are exerted thereon. To the side of these notches for the insertion of the blades are generally located one or two notches for the insertion of the locks, which make it possible to insert the lock(s) into the peripheral groove for locking the blades in a circular fashion.
Said locks generally comprise, as disclosed in the patent FR 28101366 of the applicant, a part which bears against the base of the peripheral groove and on the platforms of the last blades introduced to provide the locking thereof in circular translation, and a clamping means, such as a screw, which is accessible from the outside of the groove. To this end, a cutout is generally formed in the platform of the last blades introduced, so as to obtain access for the clamping tool. As a result, at least two blades of the compressor, and more generally four when a lock is arranged on each side of the notch for the insertion of the blades, are different from the other blades of the compressor stage.
The drawbacks associated with this configuration are, firstly, that the interchangeability of the blades is hindered, with the result that two reference points have to be dealt with and, secondly, the requirement of making at least two notches in the shoulders of the peripheral groove, one for the notch for the insertion of the blades and one, or even two, for the notch(es) for the insertion of the locks. Many more milling operations have to be carried out, therefore, and associated therewith, there is the additional risk of the rejection of parts in the event of poorly executed milling operations, which are particularly awkward to carry out.
The patent application EP 1650405 is also known, said patent application disclosing a system for immobilizing the blades in translation in the groove of the hub, using a system of bolts which pass through the groove and are fixed to the radial extensions of the shoulders of the hub. The number of bolts required in this configuration is particularly high and the system for immobilization is held via drilled holes in the shoulders of the hub.